{"schemaVersion":1,"id":"en-video-atp-system","type":"video","pillar":"energy","locale":"en","translationGroupId":"video-atp-system","slugPath":"videos/the-atp-phosphocreatine-system","title":"The ATP–phosphocreatine system — the video","shortTitle":"ATP and phosphocreatine","summary":"An animation that follows one ATP molecule through a short, intense effort and then through the rest that follows: it is spent, recharged by phosphocreatine, and backed up by the other pathways. The page carries the same content in text, with its sources and limits.","level":"intermediate","estimatedMinutes":8,"synonyms":["ATP","phosphocreatine","creatine phosphate","alactic anaerobic pathway","muscle energy"],"blocks":[{"id":"b1","type":"paragraph","content":[{"kind":"text","value":"Every muscle contraction spends the same currency: ATP. The cell keeps very little of it in reserve, and yet the effort carries on. The video shows why, by following a single molecule through a sprint and then through the rest that follows."}]},{"id":"b2","type":"videoLesson","videoId":"atp-phosphocreatine","title":"The ATP–phosphocreatine system"},{"id":"b3","type":"heading","level":2,"text":"What the video shows","anchor":"what-the-video-shows"},{"id":"b4","type":"paragraph","content":[{"kind":"text","value":"The animation opens on a schematic muscle cell. One molecule of "},{"kind":"term","value":"ATP","definition":"adenosine triphosphate, a molecule whose broken bond releases the energy used by muscle contraction"},{"kind":"text","value":" moves into contact with the contractile filaments, gives up one of its phosphate groups, and becomes ADP. The movement happens; the currency has been spent."}]},{"id":"b5","type":"paragraph","content":[{"kind":"text","value":"The shot then widens onto the reserve available. It is visibly tiny: the video draws it as a handful of molecules, used up within a few contractions. This is the central point of the sequence — the cell does not store energy as ATP, it manufactures it continuously."}]},{"id":"b6","type":"paragraph","content":[{"kind":"text","value":"Then comes phosphocreatine. A second molecule approaches the ADP, hands back a phosphate group, and rebuilds the ATP straight away. No intermediate step, no oxygen consumed: it is the fastest route the muscle has. The video repeats that transfer several times, until the phosphocreatine store falls in its turn."}]},{"id":"b7","type":"paragraph","content":[{"kind":"text","value":"The closing shot overlays three curves in different colours, which rise and fall together rather than taking over from one another. The video ends on the rest period: at rest, the transfer runs the other way and phosphocreatine is rebuilt from the ATP produced by aerobic metabolism."}]},{"id":"b8","type":"comparison","title":"Three routes, one product","columns":["Route","Speed of supply","Total capacity","Oxygen required"],"rows":[{"label":"ATP–phosphocreatine","cells":["The fastest","The smallest","No"]},{"label":"Glycolysis","cells":["Fast","Intermediate","No"]},{"label":"Aerobic metabolism","cells":["The slowest to ramp up","The largest","Yes"]}]},{"id":"b9","type":"heading","level":2,"text":"Why the recharge matters as much as the spending","anchor":"why-the-recharge-matters-as-much-as-the-spending"},{"id":"b10","type":"paragraph","content":[{"kind":"text","value":"The least intuitive part of the video is the ending, not the opening. Phosphocreatine is not a fuel that gets burned: it is a rechargeable buffer. How far it is rebuilt during recovery periods shapes the quality of the next effort, which explains why the length of the rest between sets changes the feel of a session of short efforts so much."}]},{"id":"b11","type":"evidence","level":"established","statement":"Phosphocreatine acts as a buffer store that regenerates ATP almost instantly, then rebuilds itself during recovery.","detail":"Reviews of how the metabolic routes interact describe this phosphate group transfer as the fastest source of ATP in skeletal muscle, and its resynthesis as a process that depends on oxidative metabolism during rest. The rates measured vary with fibre type, with the muscle studied and with the method used; the data most often come from maximal efforts performed in a laboratory.","referenceIds":["baker2010"]},{"id":"b12","type":"heading","level":2,"text":"Pathways that overlap rather than take turns","anchor":"pathways-that-overlap-rather-than-take-turns"},{"id":"b13","type":"paragraph","content":[{"kind":"text","value":"The classic picture of three pathways handing over to one another is convenient, but the video corrects it explicitly with its three overlapping curves."}]},{"id":"b14","type":"evidence","level":"established","statement":"During a maximal effort, the anaerobic and aerobic routes contribute at the same time, and the aerobic share becomes dominant earlier than the classic account suggests.","detail":"A review of energy system interaction reports that, during continuous maximal exercise, the anaerobic and aerobic contributions even out within a few tens of seconds, with values that vary with the protocol, the ergometer and the participants' level. The studies gathered involve healthy adults and continuous efforts: they do not directly describe a resistance session broken up by rest periods.","referenceIds":["gastin2001"]},{"id":"b15","type":"heading","level":2,"text":"The linked scene","anchor":"the-linked-scene"},{"id":"b16","type":"scene3d","sceneId":"cycle-atp-pcr","title":"The ATP–phosphocreatine cycle","intro":"The scene takes the phosphate group transfer shown in the video and lets you explore it step by step, in both directions: spending during the contraction, recharging during the rest. Every step is described in text below the scene and stays understandable without displaying the model.","accessibility":{"textAlternative":"Circular diagram: a pale ring carries three stations linked by arrows running anticlockwise. At the top, ATP is drawn as a large adenosine sphere followed by three small phosphate spheres; at the bottom left, ADP carries only two of them and a detached phosphate floats alongside; at the bottom right, phosphocreatine hands over its phosphate and leaves a creatine sphere behind. To the right of the circle, six discs stacked on a spindle represent the phosphocreatine store: the four thick discs at the bottom are still available, the two thin discs at the top have already been used, and an arrow links the store to the resynthesis station. A small marker travels around the ring to follow the cycle. The volumes are symbolic: neither the shape nor the size of the molecules is depicted.","structures":[{"label":"ATP","description":"Adenosine triphosphate carries three phosphate groups. It is the form of energy a muscle fibre uses directly in order to contract.","href":"/en/energy/atp-and-phosphocreatine"},{"label":"ADP and free phosphate","description":"When ATP gives up a phosphate, ADP and a free phosphate are left behind and the energy of the bond becomes available. The cell then has to rebuild ATP.","href":"/en/energy/atp-and-phosphocreatine"},{"label":"Phosphocreatine","description":"Phosphocreatine stored in the muscle hands its phosphate to ADP, which rebuilds ATP almost immediately. What remains is creatine.","href":"/en/energy/atp-and-phosphocreatine"},{"label":"Phosphocreatine store","description":"The stack stands for a limited store: the solid discs are still available, the pale ones have already been used. It is rebuilt during recovery.","href":"/en/energy/atp-and-phosphocreatine"},{"label":"Creatine","description":"Once its phosphate has been handed over, creatine is what remains. It is phosphorylated again when the effort stops and energy becomes available.","href":"/en/energy/atp-and-phosphocreatine"}],"steps":[{"id":"boucle","title":"1. A loop, not a line","body":"Cellular energy runs in a closed loop: ATP is spent, then rebuilt. A muscle stores almost no ATP in advance; it recycles it continuously."},{"id":"atp","title":"2. ATP, the energy currency","body":"ATP carries three phosphates, shown here as three small spheres in a row. It is the only form of energy the contractile proteins can use directly."},{"id":"hydrolyse","title":"3. One phosphate is released","body":"By releasing its third phosphate, ATP becomes ADP and frees the energy that powers contraction. The detached phosphate stays available inside the cell."},{"id":"resynthese","title":"4. Phosphocreatine recharges ATP","body":"Phosphocreatine transfers its phosphate to ADP: ATP is rebuilt almost instantly, without oxygen. It is the fastest route a muscle has."},{"id":"reserve","title":"5. A short-lived store","body":"The stack of discs stands for the phosphocreatine store: it supports a very short, very intense effort, then runs down. It is rebuilt during recovery, once the other pathways take over."}],"license":"Shapier — Propriétaire — usage interne ShapierLab"}},{"id":"b17","type":"callout","tone":"limit","title":"What the video simplifies","content":[[{"kind":"text","value":"Molecules are drawn as solid objects of comparable size, which they are not. Where they sit in the cell is schematic too."}],[{"kind":"text","value":"The animation leaves out the detail of the mitochondria, the fate of hydrogen ions, and the exchanges between the muscle and the rest of the body during effort."}]]},{"id":"b18","type":"sourceList","title":"Sources for this video","referenceIds":["gastin2001","baker2010"]},{"id":"b19","type":"relatedContent","title":"Read next","targetIds":["en-mechanism-atp-phosphocreatine","en-mechanism-muscle-glycogen","en-pathway-energy-recovery-path"]},{"id":"b20","type":"shapierAction","actionId":"deload-recuperation","label":"Read the advice on recovery weeks","description":"Read in Shapier the advice page that explains how to place lighter weeks and rest periods within a training progression.","webTarget":"https://shapier.app/en/conseils/deload-semaines-recuperation","appTarget":"shapier://conseils/deload-semaines-recuperation"}],"relations":[{"type":"explains","targetId":"en-mechanism-atp-phosphocreatine"},{"type":"next-step","targetId":"en-mechanism-muscle-glycogen"},{"type":"shapier-action","targetId":"planning-recovery"}],"authors":["equipe-editoriale-shapier"],"reviewers":["Thanh Chau"],"references":[{"id":"gastin2001","authors":"Gastin PB","year":2001,"title":"Energy system interaction and relative contribution during maximal exercise","source":"Sports Medicine","kind":"review","doi":"10.2165/00007256-200131100-00003"},{"id":"baker2010","authors":"Baker JS, McCormick MC, Robergs RA","year":2010,"title":"Interaction among skeletal muscle metabolic energy systems during intense exercise","source":"Journal of Nutrition and Metabolism","kind":"review","doi":"10.1155/2010/905612"}],"review":{"publishedAt":"2026-08-02","reviewedAt":"2026-08-02","reviewDueAt":"2027-08-02","evidenceLevel":"established"},"limitations":["The animation shows a schematic muscle cell: the proportions between molecules, organelles and distances are chosen for legibility, never drawn to scale.","The studies cited involve maximal efforts performed in a laboratory by healthy adults; the durations observed vary with the protocol, the muscle tested and the training level.","Splitting metabolism into three \"pathways\" is a teaching convention: the metabolic routes run at the same time rather than one after the other."],"seo":{"title":"ATP and phosphocreatine on video — energy for short efforts","description":"Video and text explanation of the ATP–phosphocreatine system: instant recharge, how the energy pathways overlap during a maximal effort, and the limits of the model.","canonicalPath":"/en/videos/the-atp-phosphocreatine-system","image":"/og/en/video-atp-system.png"},"app":{"offlineEligible":true},"version":1}